An Assessment of the Environmental Impacts at the Farm Scale of Three Organic Dairy Systems

ABSTRACT

The local environmental impacts of three typical organic dairy farming systems were assessed using simulated models of 100 ha, organic dairy farming units. Environmental impacts on soils, the atmosphere and waterways were estimated using published and calculated relationships. In brief, the three organic dairy farming systems were: GRS, an all grassland system where all feed concentrates were imported onto the farm: GFC, a grassland based system supported by additional forage crops and some concentrates imported onto the farm: GFF, a grassland based system with additional forage crops but with no concentrates imported onto the farm and only home-grown cereals and protein feeds used. No detrimental effects on soil organic matter, biological activity, structure or erosion risk were envisaged with any of the three systems since they all maintain at least 70% of the land as grassland. The impact of local activity on the global atmosphere was estimated at 385, 420 and 337 t of CO₂ equivalent release for GRS, GFC and GFF, respectively. Since all three systems were considered low-risk management strategies, few problems were estimated with regard to nitrate leaching, phosphorus release or human pathogen contamination of waterways from any of the systems. It is concluded that in general there is little to choose between the organic dairy farming systems assessed with regard to their environmental impact. However, as systems become more intensive with higher stocking rates and more imported nutrients, then there is greater potential for nutrients to ‘leak’ from the system and adversely impact both the local and wider environment.